The New York Times checked 600 pages of schedules in the former Mayor's archives. For the three months they looked at -- from September 17 to December 16, 2001 -- Mr Guiliani was only at Ground Zero for a total of 29 hours (click image to see NYT grapic of Mr Guiliani's visits). From the NYT:
The 29 hours Mr. Giuliani spent at ground zero involved 41 appearances, mostly to give tours to other officials and foreign dignitaries. Many entries include meetings away from the site before the tour. For instance, the schedule included 30 minutes on Nov. 15, 2001, for President Vladimir Putin of Russia, but Mr. Putin’s tour of ground zero was widely reported to have lasted 13 minutes.
The recovery people routinely worked 12-hour shifts, day in and day out, at the scene. Some NYC police dectiectives reportedly put in as many hours as Mr Giuliani in the first two days after the attack -- and averaged 400 hours over the three month period. (NYT)